Roller pair type continuous casting apparatus

ABSTRACT

In the continuous casting of a metallic band or strip, more particularly of steel, by injecting the molten metal between two cooled cylinders which are rotated in such manner that the facing portions of their peripheries move in unison in the direction of injection, the cast strip is maintained on the periphery of one of the cylinders until it is substantially fully solidified. The pressure head at the outlet of the injection nozzle corresponds to a level of molten metal situated above the nip of the cylinders. The inner side of the lateral cheeks which prevent the molten metal from flowing laterally is heated to prevent substantial solidification of the edges of the strip before same has passed through the nip. The cast strip is cooled on the cylinder on which it is maintained, as for instance by a water spray. The other cylinder is continuously lubricated to prevent sticking of the cast strip thereon. In a modification the horizontal axes of the cylinders are in a non horizontal plane, the cast strip being maintained against the lower cylinder.

United States Patent 1 [11] 3,730,254 Namy 51 May 1, 1973 ROLLER PAIR TYPE CONTINUOUS CASTING APPARATUS 75 Inventor: Philippe Namy, Saint-Etienne,

France [73] Assignee: Creusot-Loire, Paris (Seine), France 221 Filed: Dec. 18, 1970 [21] Appl. No.: 99,426

[52] US. Cl. ..164/268, 164/277, 164/338, 164/155 [51] Int. Cl. ..B22d ll/06 [58] Field of Search ..l64/73, 87, 268, 164/277, 338

[56] References Cited UNITED STATES PATENTS 3,038,219 6/1962 Hudson ..l64/88 3,351,126 11/1967 Richards et a1.... 164/278 2,127,515 8/1938 l-lazelett ..l64/277 X 2,790,216 4/1957 Hunter 1 64/277 X 2,912,321 11/1959 Brennan ..l64/87 X 3,322,184 5/1967 Cofer et a1 1 64/87 X 3,405,757 10/1968 Harvey et a1. 1 64/87 3,498,362 3/1970 Lewis 164/87 FORElGN PATENTS OR APPLlCATlONS Primary Examiner-R. Spencer Annear Attorney-Alexander & Dowel] 5 7 ABSTRACT In the continuous casting of a metallic band or strip, more particularly of steel, by injecting the molten metal between two cooled cylinders which are rotated in such manner that the facing portions of their peripheries move in unison in the direction of injection, the cast strip is maintained on the periphery of one of the cylinders until it is substantially fully solidified. The pressure head at the outlet of the injection nozzle corresponds to a level of molten metal situated above the nip of the cylinders. The inner side of the lateral cheeks which prevent the molten metal from flowing laterally is heated to prevent substantial solidification of the edges of the strip before same has, passed through the nip. The cast. strip is cooled on the cylinder on which it is maintained, as for instance by a water spray. The other cylinder is continuously lubricated to prevent sticking of the cast strip thereon. In a modification the horizontal axes of the cylinders are in a non horizontal plane, the cast strip being maintained against the lower cylinder.

5 Claims, 5 Drawing Figures Patented May l, 1913 3,130,254 7 2 Sheets-Sheet 1 Patented May 1, 1973 2 Sheets-Sheet 2 INVENTOR.

ROLLER PAIR TYPE CONTINUOUS CASTING APPARATUS The present invention relates to the continuous casting of metals such as steel.

It is known to produce a flat metallic band or strip by injecting upwardly a molten metal between two cooled cylinders having spaced parallel axes substantially disposed in a common horizontal plane, these cylinders being rotated in such manner that the facing portions of their peripheries move upwardly at the same linear speed. The molten metal is injected below the nip of the cylinders by means of a flat refractory nozzle connected with a feed tundish and lateral blocks or cheeks are provided to retain between the cylinders the metal which issues from the nozzle. The operating conditions are so selected that the level of the molten bath within the feed tundish is situated somewhat below the horizontal plane defined by the cylinder axes (i.e. below the nip of the cylinders), and that the metal is substantially completely solidified before reaching the said plane so as to be noticeably compressed or compacted between the cylinders, somewhat as in a rolling mill.

With hard metals, such as steel, this method or machine has the disadvantage that the periphery of the cylinders, generally made of copper, is rapidly damaged owing to the erosion which results from their rolling action on the solidified steel band or strip. It is to be noted in this respect that even if the inner portion or core of this band or strip is still quite hot and somewhat plasticin the nip of the cylinders, its superficial portion or skin which is in contact with the cooled periphery of the cylinders is cold and hard. Moreover the temperature of the core is not perfectly uniform, and relatively cold and hard zones may appear, which is highly detrimental to the relatively soft periphery of the cylinders.

It is an object of the present invention to avoid these inconveniences of the prior art. i

Another object of the invention is a method and a machine of the kind above referred to wherein the level of the molten metal in the feed tundish is situated above the nip of the cylinders, the operating conditions being such that the band or strip is only completely solidified above the said nip.

Still a further object of the present invention is a method and a machine of the kind above referred to, wherein the strip or band issuing from the nip of the cylinders is maintained in contact with the periphery of one of the said cylinders until it is completely solidified, and is then removed from this periphery as for instance by a scraper blade. The cooling of the band or strip on the corresponding cylinder may be assisted by spraying a cooling fluid thereon.

The inner wall of each of the lateral cheeks which maintain the molten metal between the cylinders preferably comprises an inwardly protruding vertical rib provided with inner heating means, as for instance an electric resistance, this rib terminating somewhat below the horizontal plane defined by the axes of the cylinders. The edges of the band or strip are thus kept in the molten state and the liquid metal may flow FIG. 1 is a general side view with parts in section diagrammatically illustrating a machine constructed in accordance with the present invention.

FIG. 2 is a large-scalefragmental cross-section of the cylinders of this machine in the zone of the nip of the cylinders.

FIG. 3 is a section of the feeding portion of the machine. I

FIG. 4 is a large-scale fragmental section of the injecting nozzle, corresponding to the line IVIV of FIG. 2.

FIG. 5 is a diagrammatical side view of a-modified embodiment of a machine according to the invention.

With reference to the somewhat diagrammatical illustration of FIG. 1, in an embodiment of the present invention a machine for the continuous casting of metals, and more particularly of steel, comprises two cylinders l and 2 respectively carried by parallel shafts 3 and 4 having their axes substantially situated in the same horizontal plane, at such a distance from each other as to define a relatively narrow nip 0 (FIG. 2) between the cylinders. The cylinders (or at least their peripheries) are preferably made of copper and they are conveniently cooled by means not illustrated, as for instance by an inner circulation of an appropriate liquid such as water. Shafts 3 and 4 are rotated at the same speed but in opposed direction in such manner that in the zone of the nip a their facing peripheries move upwardly. An upwardly opening flat injection nozzle 5, made of a highly refractory material such as graphite, is disposed between cylinders 1 and 2, below their nip a (FIG. 2). This nozzle is connected by a lower I 7 horizontal canal 6 (FIG. 3) with a heat-insulated feed tundish 7. Lateral cheeks 8 (FIG. 4), also made of graphite or like highly refractory material, are pressed against the lateral sides of cylinders 1 and 2 by springs 9 which rest against stationary members 10 of the machine frame. Checks 8 are appropriately guided, as for instance by gudgeons 11 which slide through members 10. Each cheek 8 extends substantially in the zone comprised between the base of nozzle 5 and nip a. Its inner side has a recess 8a in which is disposed an electric heating resistance 12 covered by a vertically elongated cover 13 which terminates immediately below mp a.

In operation the level within tundish 7 is maintained in a horizontal plane A-A situated somewhat above the nip a of cylinders 1 and 2 (see FIG. 2). Stated in other words, the molten metal is injected between the cylinders under a ferrostatic pressure which corresponds to the said level A-A, in contradistinction to the prior art wherein this level is kept below the said nip. By properly selecting the peripheral speed of cylinders 1 and 2 in the nip a, the flat metallic mass or strip confined between the cylinders and the lateral cheeks is formed of a still liquid core comprised between two thin sheets or skins which have solidified in contact with the cool peripheries of the cylinders, Owing to the presence of resistances 12, the edges of this mass or strip are still highly plastic and impart no local compressive force against the cylinders which are not there fore unduly eroded. The strip which issues upwardly from nip a is more or less similar to a flat thin-walled tube enclosing a liquid mass and it would break if it were vertically pulled upwardly as in known machines.

In accordance with the present invention it is therefore retained against one of the cylinders (cylinder 1 in the example illustrated), as indicated at S, until it is substantially fully solidified. It is then removed from cylinder 1 by a scraper 14 and is passed through pairs of pulling and straightening rollers 15 and 16 before reaching a heat-treating furnace 17 wherein it is supported by rollers 18. It thereafter passes between heating elements 19 and is rolled by the cylinders 20 of a rolling mill 21. The lateral sides of the rolled strip are trimmed by circular shears 22 and the strip is wound as indicated at 23.

In order to assist the cooling of the strip S on cylinder 1, water is sprayed thereon by appropriate sprayers 24,

the steam formed being evacuated through a hood 25. Downstream of scraper 14 the periphery of cylinder 1 is cleaned by water sprayers 26 and by a cylindrical rotating brush 27 before returning towards the casting zone.

As to cylinder 2, its periphery is also cleaned by water sprayers 28 and by a rotating brush 29, and it is thereafter lubricated by means of an appropriate coating roller 30 to which grease or oil is continuously supplied by appropriate means, not illustrated. Owing to this lubrication of cylinder 2, the cast strip S adheres preferentially to the non-lubricated cylinder 1. It is further to be noted that owing to the contraction due to its cooling on the periphery of cylinder 1, the strip becomes almost fully disengaged by itself from this cylinder before reaching the scraper 14.

It is of course important for a satisfactory operation, to closely control the rotational speed of the cylinders in order, to obtain for the strip an outer skin of the proper thickness in the nip a. If this skin is too thick, the compressive reactions on the cylinders may become too high and erosion of their periphery may appear. If the skin is too thin, it may break immediately above nip a and the whole continuous process may be ruined. In accordance with the present invention proper control of the rotational speed of the cylinders may be effected by two methods, namely either by measuring the superficial temperature of the strip immediately above nip a (as for instance by optical processes), or by determining the reaction of the strip on the cylinders (the bearings of the shaft of cylinder 2 may be mounted in slides retained in position by appropriate spring means, the quite small displacements of these slides being proportional to the said reaction). It is also possible to rely on the shape of the product above the nip. When the skin is too thin, the free side of the strip bulges noticeably under the action of the pressure of the still liquid core.

As to the control of the level of molten metal within the tundish 7, it may be effected by any appropriate means and more particularly by those which are used for maintaining the level of molten metal in the cooled vertical mould of the conventional continuous casting apparatus wherein a solid bar is continuously extracted downwardly from such a mould which receives the metal in liquid form from an appropriate supply. In FIG. 3 there has been illustrated for this purpose a well known device comprising a photo-electric cell 31 which is disposed laterally so as to receive an increased amount of radiation from the surface of the bath 32 within tundish 7 as the level rises. The signal from cell iii 31 is applied to a transducer circuit 33 which derives therefrom an actuating signal. The latter controls a motor 34 adapted to rotate in one or the other direction a tilting ladle 35 which pours molten metal into tundish 7 so as to maintain the level therein to a substantially constant height during operation of the casting machine.

Experience has demonstrated that the cooling effect of the cylinders on the molten metal just below their nip a,i.e., the formation of the outer skin of the strip S of FIG. 1, is almost exclusively ensured by the immediate absorption of latent heat by the cool periphery of the cylinders, heat evacuation by the inner cooling water being too slow for this purpose. It has further been noted that this quick cooling of the outer skin has a favorable quenching action on the metal itself. It is therefore of interest to bring this periphery to a very low temperature just before it reaches the casting zone. This is normally obtained by the inner water circulation, but in some cases the temperature of the periphery may be lowered well below the outer temperature by means of a refrigerating agent, such as a liquefied gas, used either as the inner cooling fluid, or in the form of a bath in which the lower portion of each cylinder is immersed, or further by spraying the said agent on the periphery of the cylinders.

In the embodiment diagrammatically illustrated in FIG. 5 the axes of the shafts 43 and 44 of the cylinders 41 and 42 are disposed in a plane BB which is at an acute angle a with respect to the vertical. The injection nozzle 45 is of course at the same angle a to the horizontal. But here again the level within the feed tundish 47 is slightly above the nip a of the cylinders. The cast strip S is retained against the lower cylinder 41 (on which it besides tends to rest under the effect of gravity). It is removed therefrom almost vertically (gravity here again assisting the operation). The solidified, but still somewhat plastic strip passes under a roller 48 from which it is returned horizontally towards the other processing apparatus. Though this has not been illustrated, the machine of FIG. 5 may comprise the same auxiliary devices as the machine of FIG. 1 (water sprayers, rotating brushes, lubricating roller).

The above-mentioned angle a may vary between (in which case the axes of the cylinders are situated in the same horizontal plane, as in FIG. 1) and 0 (which corresponds to an embodiment somewhat as in FIG. 5, but with cylinder 42 disposed exactly above cylinder 41, i. e. with the axes of these cylinders in the same vertical plane). It is to be noted that as it decreases, the strip S is more effectively supported, while the pressure head generated by the still liquid core is of lesser importance.

Iclaim:

1. A machine for the continuous casting of a strip from a molten metal, comprising:

a first and a second cooled cylinders of substantially same diameter having parallel axes situated in the same horizontal plane and having peripheries which determine between them a nip, said cylinders rotating substantially at the same peripheral linear speed and in the same peripheral direction in said nip to thus define for said nip a lower inlet end and an upper outlet end;

a nozzle having an outlet opening into the inlet and of said nip to inject from below the nip the molten metal into said nip to form the cast strip by solidification of said molten metal,

a feed tundish connected with said nozzle to supply molten metal thereto;

means to maintain in said tundish a bath of molten metal at a substantially constant lever and at a ferrostatic head corresponding to a level situated above the nip of the cylinders, whereby the pressure head at the outlet of said nozzle corresponds to a level of said molten metal situated above said means to continuously coat the periphery of said second cylinder with a lubricating substance to cause said strip to preferentially stick to the periphery of said first cylinder;

and means to remove said strip in fully solidified state from the periphery of said first cylinder at a distance from said nip.

2. In a machine as claimed in claim 1:

said first and second cylinders having flat lateral sides;

and said machine further comprising two stationary lateral cheeks each having an inner side substantially applied against one of the lateral sides of said first and second cylinders to prevent molten metal injected by said nozzle from flowing laterally of the peripheries of said first and second cylinders, and means to heat the inner side of each of said cheeks in the zone thereof situated between said nozzle and said nip to prevent solidification of said molten metal against said inner side. I 3. In a machine as set forth in claim 2, said cheeks protruding laterally in part into said nip.

4. A machine for the continuous casting of a strip from a molten metal, comprising:

a pair of cooled cylinders of substantially same diameter having parallel axes situated in substantially the same horizontal plane and having peripheries which determine between them a nip, said cylinders rotating substantially at the same peripheral linear speed and in the same peripheral direction in said nip to thus define for said nip a lower inlet end and an upper outlet end, and said pair of cylinders having substantially flat lateral sides; a nozzle having an outlet opening into the inlet end of said nip to inject from below the nip the molten I metal into said nip to form the cast strip by solidification of said molten metal;

a feed tundish connected with said nozzle-to supply 

1. A machine for the continuous casting of a strip from a molten metal, comprising: a first and a second cooled cylinders of substantially same diameter having parallel axes situated in the same horizontal plane and having peripheries which determine between them a nip, said cylinders rotating substantially at the same peripheral linear speed and in the same peripheral direction in said nip to thus define for said nip a lower inlet end and an upper outlet end; a nozzle having an outlet opening into the inlet and of said nip to inject from below the nip the molten metal into said nip to form the cast strip by solidification of said molten metal, a feed tundish connected with said nozzle to supply molten metal thereto; means to maintain in said tundish a bath of molten metal at a substantially constant lever and at a ferrostatic head corresponding to a level situated above the nip of the cylinders, whereby the pressure head at the outlet of said nozzle corresponds to a level of said molten metal situated above said nip; means to continuously coat the periphery of said second cylinder with a lubricating substance to cause said strip to preferentially stick to the periphery of said first cylinder; and means to Remove said strip in fully solidified state from the periphery of said first cylinder at a distance from said nip.
 2. In a machine as claimed in claim 1: said first and second cylinders having flat lateral sides; and said machine further comprising two stationary lateral cheeks each having an inner side substantially applied against one of the lateral sides of said first and second cylinders to prevent molten metal injected by said nozzle from flowing laterally of the peripheries of said first and second cylinders, and means to heat the inner side of each of said cheeks in the zone thereof situated between said nozzle and said nip to prevent solidification of said molten metal against said inner side.
 3. In a machine as set forth in claim 2, said cheeks protruding laterally in part into said nip.
 4. A machine for the continuous casting of a strip from a molten metal, comprising: a pair of cooled cylinders of substantially same diameter having parallel axes situated in substantially the same horizontal plane and having peripheries which determine between them a nip, said cylinders rotating substantially at the same peripheral linear speed and in the same peripheral direction in said nip to thus define for said nip a lower inlet end and an upper outlet end, and said pair of cylinders having substantially flat lateral sides; a nozzle having an outlet opening into the inlet end of said nip to inject from below the nip the molten metal into said nip to form the cast strip by solidification of said molten metal; a feed tundish connected with said nozzle to supply molten metal thereto; lateral cheeks each having an inner side substantially applied against one of the lateral sides of said pair of cylinders; and means to heat the inner side of each of said cheeks in the zone thereof situated between said nozzle and said nip to prevent solidification of said molten metal against said inner side.
 5. In a machine as set forth in claim 4, said cheeks protruding laterally in part into said nip. 